In many manufacturing operations and process control operations, the accurate measurement of temperatures are often required. However, in such industrial environments, precision temperature measurements are difficult to obtain.
In an attempt to resolve this problem and provide industrial manufacturers with systems for accurate temperature measurements, prior art equipment has been developed. One such major advance was the development of resistance temperature detectors (RTDs) for industrial use. These RTDs are immersed in the medium, the temperature of which is to be measured, and produce an output voltage which is a direct measuring resistance, which is a direct function of the temperature being measured. Then, using either a standard table of values or the quadratic equation which represents the relationship between the resistance and the temperature, the actual temperature is determined.
Although these prior art resistance temperature detectors are conventionally employed to provide accurate temperature measurement, and platinum RTDs have become the standard in the industry, the measurements attained are not sufficiently accurate for many applications, due to various inherent difficulties with proper calibration, drift, component aging, undetected resistance levels in the electrical leads, and accurate conversion of resistance to temperature by the operator.
In an attempt to eliminate these inherent difficulties with precision temperature measurements by resistance temperature detectors alone, other prior art systems have been developed which incorporates electronic processing equipment to compensate for the known variables in the resistance temperature detectors, while also converting the resistance value produced to the corresponding temperature. The principal system of the nature is shown in U.S. Pat. No. 4,122,719 issued Oct. 31, 1978, wherein a microprocessor is employed to eliminate measurement errors and provide the requisite calculations to achieve an accurate temperature measurement. However, the system disclosed in U.S. Pat. No. 4,122,719 is extremely expensive and requires operator calibration and monitoring. Consequently, the cost of operating such equipment is also very high.
It is the principal object of the present invention to provide a temperature measuring system which is capable of achieving precision temperature measurements while being comparatively inexpensive to manufacture, install and operate.
Another object of the present invention is to provide a precision temperature measuring system having the characteristic features defined above which is capable of determining temperature measurements over a pre-selected limited temperature range.
Another object of the present invention is to provide a precision temperature measuring system having the characteristic features defined above which operate automatically, with a minimum of operator control or supervision, and continuously displays and updates a plurality of temperatures.
Other and more specific objects will in part be obvious and will in part appear hereinafter.